Retractable bearing shoes for caissons



March 24, 1959v F. c. JACOBS 2,378,649

RETRACTABLE BEARING sHoEs FOR cAIssoNs v Filed May 19, 1954 2sheets-Sheet 1 F. c. JACOBS RETRACTABLE BEARING SHOES FOR CAISSONS March24, 1959 l United States Patent O 878,649 RETRACTABLE BEARING sHoEs FoncAIssoNs Frank C. Jacobs, Water Proof, La., assignor, by mesneassignments, to California Research Corporation, San Francisco, Calif.,a corporation of Delaware Application May 19, 1954, Serial No. 430,882

2 Claims. (Cl. 61-46.5)

The present invention relates to a method of and apparatus forestablishing a portable marine foundation of the caisson type, moreparticularly relates to a method of and apparatus for increasing theload-carrying capacity of a caisson in an unstable foundation bed tosupport an offshore drilling structure, and has for an object theprovision of a structure adapted for deep water drilling which may bestabilized in an unstable foundation bed by providinglaterally-extending, supporting shoes adapted to be extended andretracted within the over-all dimensions of the caisson.

In the drilling of oil wells in offshore locations where the water depthis from a few feet up to about 100 feet and the bottom is unstable, ithas been found extremely diicult to provide a portable marine foundationwhich may be floated to the drilling location and then extendedsuciently deep into the unstable bottom, with a suliicient length of thecaisson extending above water, to permit a drilling deck to be placedabove wave height under storm conditions. The primary diiculty has beenthat the caissons or piles upon which the structure is supported must bedriven into the unconsolidated bottom to the refusal point. That is, thepiles are driven until they will not go deeper under a predeterminedload. Such refusal point in many instances is so deep, withpreviously-known forms of equipment, that the depth of water in whichdrilling may be done has either been seriously restricted, due to thelength and weight of the caissons, or the entire structure renderednon-portable after erection.

In accordance with the present invention, there is provided a method ofstabilizing a caisson, adapted to support a structure above abnormalwave heights and capable of supporting the complete drilling structureon an unstable bottom, without undue lengthening of the caisson. In apreferred form of apparatus for carrying out the present method, aplurality of retractable plate, or shoe, members adapted to form spreadfootings for said caisson are spaced equally around the periphery of thecaisson and held in a retracted position both during the lowering of thecaiss-on intolengagement with the underwater bottom and during thefurther vertical loading of the caisson to obtain lateral stability forsaid caisson in the underwater foundation material. Further inaccordance with the invention, the retractable shoes may be forcedoutwardly into the foundation material to provide a greatly increasedload-carrying area adjacentV the lower part of the caisson, after thedesired depth of the underwater formation has been penetrated. lettingmeans may be provided for the laterally-extendible shoe members toassist in the extension thereof into the unstable media forming'thefoundation bed. Following the drilling of a well from a platformsupported by caissons having the spread-footing shoes, the shoes may beretracted within the confines of the caisson periphery to permit thecaisson to be withdrawn from bottom and again supported n a oatablestructure for movement to another drilling site.

Further objects and advantages of the present invention willbecomeapparent from the following detailed descripv2,878,649 Patented Mar. 24,1959 2 tion, taken in conjunction with the accompanying drawings.

In the drawings:

Fig. 1 is an offshore drilling structure adapted to be supported uponcaissons provided in accordance with the present invention withload-carrying, retractable shoe members, with said members beingillustrated in their extended position.

Fig. 2 is a top plan View of the lower end of the caissons illustratedin Fig. 1, further illustrating a preferred form of the invention.

Fig. 3 is a side elevation of the lower end of a caisson, partiallybroken away, to illustrate the operating mechanism for the retractableshoes.

Fig. 4 is a detailed view of the hydraulic connections for the ram meansemployed in extending and retracting the shoe members.

Referring now to the drawings and in particular to Fig. l, there Aisillustrated a oatable drilling foundation identied as barge 10, capableof supporting an entire drilling structure, including derrick 11, powerdrilling equipment indicated generally as 12, drill pipe 13, andhoisting equipment 14. The barge 10 is adapted to float the completedrill rig to a desired drilling site. After floatable foundation 10 hasarrived at its intended site, a plurality of caissons indicatedgenerally as 15, normally supported by the floating structure during themoving operation, are dropped downwardly through the wells 16 in thebarge hull until the lower portion thereof engages the underwaterbottom.

In the present embodiment, caisson members 15 are adapted to be jackeddownwardly into the unstable bottom to a sufficient degree to providelateral stability for the barge hull and to bring the hull above thesurface of the water a suicient distance so that the lower portion ofthe hull will not be within the normal range of waves at thedrillinglocation. Thisdistance is, of course, quite variable dependingupon the total Weight of the platform and the load-carrying capacity ofthe bottom.

Since the total weight of the entire drilling structure progressivelyincreases as the depth of the well drilled from the foundation isincreased, due to the addition of' several tons of drill pipe which issupported by the struc ture, there is presented a serious problem inmaintaining the height of lthe structure with caissons of even quitelarge diameter where the underwater bottom is not well consolidated. Inaccordance with the present invention, the load-carrying ability 'ofthese caissons upon which the drilling structure is supported is greatlyincreased by the provision of a plurality of laterally extendible andretractable bearing shoes 17, which are adapted to be forced outwardlyinto the unstable bottom from the lower end of the caissons 15. t

An indicated, bearing shoes 17 are normally positioned within thecaisson during the lowering thereof into the bottom and then may beextended to a desired degree to provide load support so that barge 10may be raised above the water level and the barge totally supported oncaissons 15. Thus, shoes 17 provide a greatly expanded bearing load areaadjacent the bottom of the caisson so that upon increasing the weightsupported on drill barge 10 by the addition Vof drilling mud, drillpipe, and other load to the barge, the caissons need not be increased inlength and correspondingly increased in weight. This latter advantage ofthe bearing shoe 17 is of particular importance when it is consideredthat the caissons may have a diameter as great as l5 feet and that thelineal weight of such caissons may be as much as a thousand pounds perfoot of length.

entire structure depends upon the lineal length of the caissons beingheld to a minimum. In accordance with the present invention, it will beseen that the expansible bearmg shoes 17 at the lower end of each of thecaissons may more than double the bearing load area of each caisson andaccordingly reduce'the square foot loading' on the unstable bottom,wherein the caisson is posltloned.

As particularly illustrated in Fig. 2, the bearing shoes 17 .are adaptedto pass through window openings 20, which may be positioned around theperiphery of caisson 15. In the present embodiment, four shoes may belocated as illustrated, each being positioned at 90 degrees around theperiphery of caisson 15 and staggered at successive levels around thelower end of caisson 15. By this arrangement the bearing shoes may havea maximum area so that, when retracted, they are fully enclosed withincaisson 15 and, when expanded outwardly into the underwater bottom, willprovide a maximum bearing area.

Shoe 17 may be hydraulically extended and retracted by the hydraulic rammeans, indicated generally as 22. In the present embodiment, a pair ofthese hydraulic ram means 22 is provided for each of the bearing shoes17. Further, to increase the bearing area of shoes 17, ram means 22 isoperated by hydraulic connections being made thereto through theconnecting rods 25. This construction is particularly illustrated inFig. 4, in which it will be observed that the inlet conduit 27 passesthrough the head of piston means 28 to feed, or withdraw, hydraulic uidfrom the forward end of chamber 29, formed integrally with the bearingshoe 17. Fluid conduit means 30 may be connected to the rear portion 31of chamber 29 through the side of connecting rod 25, immediately behindpiston 28.

While not illustrated in detail, it will of course be understood thatcontrol valve means for regulating the iiow direction of fluid throughcondits 27 and 30 may be selectively operated to permit the extension orretraction of any of the bearing shoes 17, independently of the othershoes, or to operate simultaneously all of the shoes. Indicating means,such as lights, operated in response to the portion of the individualshoes, may be provided adjacent the control valve means.

In the extension of bearing shoes 17 to increase the load-carryingcapacity of caissons 15, jetting means are provided adjacent the leadingedge 35 of bearing shoe 17, as well as along the upper and lowersurfaces of the shoe. These jetting means are indicated generally as 36,and comprise a plurality of nozzles 37 formed in the leading edge 35 ofshoe 17 and along the upper and lower surface to communicate with achamber or header 40, to which the uid is supplied under pressure byconduit 41 adapted to pass slidably through a shaft seal 42 at the rearedge 44 of the bearing shoe 17. The jetting means may also be employedto assist in retraction of shoes 17 by relieving the suction betweensaid shoe and the formation after drilling. As illustrated, each of thebearing shoes 17 is further guided in its retraction and extension byguide rails 46 lying along the opposite sides of load-carrying shoes 17.

While the load-supporting or bearing shoes 17 have been illustrated asrelatively at members extendible, in a generally radial direction,outwardly from caisson 15, it will be understood that these extendiblemembers may be varied considerably in their configuration withoutdeparting from the invention. Such laterally-extendible members,independent of their exact configuration, will, of course, providestability for the caissons and permit said caissons to be shortenedconsiderably while at the same time retaining their load-,carryingfunction to support a fully-portable marine foundation. Accordingly, itwill be seen that there has been provided a novel method of establishinga caisson-supported, portable foundation which may be entirelyself-contained and which may be readily moved from one drilling site toanother, without construction or reconstruction at either location.

While various modifications and changes in the method and the preferredform of apparatus for carrying out that method may be made withoutdeparting from the present invention, all such modifications and changeswhich fall within the scope of the appended claims are intended to beincluded therein.

I claim:

l. A retractable bearing shoe for a caisson footing comprising a shoeelement having upper and lower walls forming respectively upper andlower planar surfaces extending transversely of the longitudinal axis ofthe caisson and slidably mounted on the caisson for extension through anopening in a peripheral wall thereof and retraction within said caisson,and end wall on said shoe element connecting said upper and lower walls,said end wall conforming in shape with the peripheral wall of saidcaisson to provide a continuous outer surface for said caisson when saidshoe element is retracted, a first chamber formed within said shoeelement and adjacent the said end wall thereof, jetting nozzles formedthrough the said walls of said shoe element and communicating with saidfirst chamber, a conduit for jetting fluid supported by said caisson inlixed relationship thereto, a second chamber in said shoe element forreceiving said conduit in telescopic relationship and .communicatingwith said first chamber, a sealing means' between the walls of saidsecond chamber and said conduit to permit said conduit to sliderelatively into and out of said second chamber in a fluid-tightrelationship, a cylinder formed within said shoe element, a pistonslidably mounted in said cylinder, a connecting rod connecting saidpiston to said caisson,

' means to introduce a pressure fluid alternately into each end of saidcylinder to move said shoe element relative to said caisson, and meansto introduce a jetting uid into said conduit.

2. A retractable bearing shoe for a caisson footing comprising a shoeelement having upper and lower walls forming respectively upper andlower planar surfaces extending transversely of the longitudinal axis ofthe caisson and slidably mounted on the caisson for extension andretraction in a plane transverse to the longitudinal axis thereof, anend wall on said shoe element connecting said upper and lower walls anddisposed adjacent the outer peripheral wall of said caisson when saidshoe element is retracted within said caisson, a chamber formed withinsaid shoe element and adjacent the said end wall thereof, jettingnozzles formed through the said walls of said shoe element andcommunicating with said chamber, means to introduce a jetting iluidunder pressure into said chamber while said shoe element is movedrelative to said caisson, a cylinder formed within saidk shoe element, apiston slidably mounted in said cylinder, a connecting rod having oneend connected to said piston and the other end connected to saidcaisson, a iluid conduit extending through said piston rod andcommunicating with one end of said cylinder, a second fluid conduitextending through said piston rod and communicating with the other endof said cylinder, and means to introduce a pressurized iluld alternatelythrough said fluid conduits to extend said shoe element outwardly of theperipheral wall of said caisson and to retract said shoe element withinsaid caisson.

References Cited in the le of this patent UNITED STATES PATENTS1,915,331 Neveling June 27, 1933 1,982,687 OBrien Dec. 4, 1934 2,468,729Black May 3, 1949 2,540,878 Hayward Feb. 6, 1951 FOREIGN PATENTS 501,464France of 1920 504,895 Great Britain of 1939 989,975 France May 30, 1951

